IIDIDispatch

IIDIDispatch refers to the interface identifier (IID) for the IDispatch COM interface used in OLE Automation. An IID is a globally unique identifier that distinguishes one interface from another across components and processes.

In Windows COM, interfaces are identified by GUIDs, and IDispatch provides a standard late-binding mechanism that automation clients can rely on. IDispatch enables dynamic method invocation and property access on COM objects, without requiring compile-time knowledge of the object’s interface.

The IID for IDispatch is {00020400-0000-0000-C000-000000000046}, typically defined in headers such as oaidl.h and oleidl.h as IID_IDispatch. IDispatch inherits from IUnknown and defines the core automation methods: GetTypeInfoCount, GetTypeInfo, GetIDsOfNames, and Invoke. These methods allow clients to obtain type information and to invoke methods or access properties by name at runtime, using either names or DISPIDs.

Usage involves a client obtaining the IDispatch interface via QueryInterface with IID_IDispatch, retrieving type information from a type library if available, mapping method names to DISPIDs with GetIDsOfNames, and calling Invoke to execute methods or access properties. This mechanism is especially important for scripting languages and automation scenarios, where late binding and language-agnostic invocation enable interoperation with COM servers without early binding.

IIDIDispatch is central to COM-based automation, facilitating cross-language interoperation and dynamic dispatch. Some environments extend IDispatch with additional capabilities through interfaces like IDispatchEx, but IDispatch remains the foundational automation interface in many COM components.